All you need to do is figure out where the little buggers are coming in at, and sprinkle a baby powder firewall. Ants that are already in your house will lose their scent trail, get lost, and eventually die; ants that are trying to come into your house won't be able to crest the mountain of white.

Just as an aside, I've also made this work with lemon-scented cleaner; apparently ants hate that lemony fresh smell. What are some ways you've gotten rid of ants? Thoughts to comments or to tips at lifehacker.com.